The present study examined the effect of bolus viscosity on the onset of laryngeal closure (relative to hyoid elevation), the duration of laryngeal closure, and other key events of swallowing in ten healthy volunteers. All volunteers underwent 320-row area detector computed tomography swallow studies while swallowing 10 ml of honey-thick barium (5 % v/w) and thin barium (5 % v/w) in a 45° reclining position. Three-dimensional images of both consistencies were created in 29 phases at an interval of 0.10 s (100 ms) over a 2.90-s duration. The timing of the motions of the hyoid bone, soft palate, and epiglottis; the opening and closing of the laryngeal vestibule, true vocal cords (TVC), and pharyngoesophageal segment; and the bolus movement were measured and compared between the two consistencies. The result showed differing patterns of bolus movement for thin and thick liquids. With thin liquids, the bolus reached the hypopharynx earlier and stayed in the hypopharynx longer than with thick liquids. Among events of laryngeal closure, only the timing of TVC closure differed significantly between the two consistencies. With thin liquids, TVC closure started earlier and lasted longer than with thick liquids. This TVC movement could reflect a response to the faster flow of thin liquids. The results suggest that bolus viscosity alters the temporal characteristics of swallowing, especially closure of the TVC.
"Swallowing motor output is modified by variations in bolus
characteristics including volume, viscosity, taste, and temperature. These
characteristics impact various biomechanical parameters of the swallow and include: 1)
duration of upper esophageal sphincter (UES) opening10,38,47,50, 2) duration
of swallow apnea9,44,45, 3) timing of
pharyngeal phase initiation and laryngeal closure16,18,49, 4) lung volume at swallow initiation112,113, 5) oropharyngeal pressure10,47,82, 6) amplitude and duration of muscle
activation17,104, and 7) total oropharyngeal swallow duration16,47,63,104. Similarly, cough motor output is modified by type of
irritant (i.e., capsaicin, citric acid, fog, brandykinin, etc.)60,81, irritant concentration13,20,25,110, volume and
duration of irritant presentation105,
nasal afferent stimulation87,116, and lung volume at cough
characteristics then result in modifications to cough inspiratory flow rate3,4,
number of coughs produced22,25,60,74,81,105,110, self-reported urge to cough21,22, amplitude and duration of expiratory muscle activation during
cough34,110, and cough expiratory airflow parameters43,60,110. "
[Show abstract][Hide abstract] ABSTRACT: Deficits of airway protection can have deleterious effects to health and quality of life. Effective airway protection requires a continuum of behaviors including swallowing and cough. Swallowing prevents material from entering the airway and coughing ejects endogenous material from the airway. There is significant overlap between the control mechanisms for swallowing and cough. In this review we will present the existing literature to support a novel framework for understanding shared substrates of airway protection. This framework was originally adapted from Eccles' model of cough28 (2009) by Hegland, et al.42 (2012). It will serve to provide a basis from which to develop future studies and test specific hypotheses that advance our field and ultimately improve outcomes for people with airway protective deficits.
Journal of applied oral science: revista FOB 07/2014; 22(4):251-260. DOI:10.1590/1678-775720140132 · 0.92 Impact Factor
"Hyoid movement makes an important contribution to laryngeal elevation, laryngeal vestibule closure, and upper esophageal sphincter opening during swallowing    . On a lateral view videofluoroscopic recording, the hyoid can be observed to move in a rapid burst in the superior and anterior directions, contributing to a net diagonal vector displacement . "
[Show abstract][Hide abstract] ABSTRACT: Hyoid movement in swallowing is biomechanically linked to closure of the laryngeal vestibule for airway protection and to opening of the upper esophageal sphincter. Studies suggest that the range of hyoid movement is highly variable in the healthy population. However, other aspects of hyoid movement such as velocity remain relatively unexplored. In this study, we analyze data from a sample of 20 healthy young participants (10 male) to determine whether hyoid movement distance, duration, velocity, and peak velocity vary systematically with increases in thin liquid bolus volume from 5 to 20 mL. The temporal correspondence between peak hyoid velocity and laryngeal vestibule closure was also examined. The results show that maximum hyoid position and peak velocity increase significantly for 20 mL bolus volumes compared to smaller volumes, and that the timing of peak velocity is closely linked to achieving laryngeal vestibule closure. This suggests that generating hyoid movements with increased power is a strategy for handling larger volumes.
[Show abstract][Hide abstract] ABSTRACT: Velopharyngeal closure plays an important role in preventing air pressure leakage during swallowing and phonation from oropharynx to nasopharynx. Levator veli palatini muscle activity is influenced by oral and nasal air pressure, volume of the swallow bolus and postural changes. However, it is unclear how velopharyngeal closing pressure is affected by reclining posture. The purpose of this study was to investigate the effects of reclining posture on velopharyngeal closing pressure during swallowing and phonation. Nine healthy male volunteers (age range, 27-34 years) participated in this study. Velopharyngeal closing pressure during a dry swallow, a 5-mL liquid swallow, a 5-mL honey-thick liquid swallow and phonations of /P∧/ and /K∧/ were evaluated in an upright posture and at reclining postures of 60° and 30°. A manometer catheter was inserted transnasally onto the soft palate, and each trial was repeated three times. A solid-state manometer catheter with an intra-luminal transducer was used to evaluate the amplitude and duration of each trial, and data were statistically analysed. Average amplitudes during dry and liquid swallows were significantly lower in reclining postures compared with the upright posture, but the amplitude was not significantly different during the thick liquid swallow. Average durations were not affected by postural changes. The amplitudes during phonations were lower in reclining postures, but the differences were not significant. Velopharyngeal closure is significantly affected by reclining posture. This suggests that velopharyngeal closing pressure may be adjusted according to afferent inputs, such as reclining posture and bolus viscosity.
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